While X-ray, ion beam, and e-beam lithography have all been demonstrated as viable next generation lithography techniques, they are, however, slow and expensive (M. Geissler, Y. Xia, Adv. Mater. 16 (15), p. 1249, 2004). Nano-imprinting lithography (NIL) offers a very attractive alternative to the fabrication of sub-micron (i.e., nanometer-scale) features, largely due to the process being simple, fast, and inexpensive, thus making it a potential technique for replacing photolithography in mass production. Although a relatively high yield has been demonstrated, the yield of imprinting relies heavily on a proper tuning of surface energy among the components, i.e., the substrate, the mold, and the polymer. An anti-adhesion layer is almost a prerequisite in NIL processes to ensure that the polymer remains on the substrate during de-molding steps. Accordingly, non-uniformity in the anti-adhesion treatment often results in poor yield (R. W. Jaszewski, H. Schift, B. Schnyder, A. Schneuwly and P. Groning, Appl. Sur. Sci. 143, pp. 301-308, 1999; S. Park, C. Padeste, H. Schift and J. Gobrecht, Microelectronic Eng. 67-68, pp. 252-258, 2003).
Although NIL techniques have successfully demonstrated an ability to fabricate multilayer structures (L. R. Bao, X. Cheng, X. D. Huang, L. J. Guo, S. W. Pang, and A. F. Yee, J. Vac. Sci. Technol. B 20, pp. 2881-2886, 2002; X. D. Huang, L. R. Bao, X. Cheng, L. J. Guo, S. W. Pang, and A. F. Yee, J. Vac. Sci. Technol. B 20 (6), pp. 2872-2876, 2002; X. Sun, L. Zhuang, W. Zhang and S. Y. Chou, J. Vac. Sci. Technol B 16 (6), pp. 3922-3925, 1998; B. Faircloth, H. Rohrs, R. Ruogg, R. R. Krchnavek, J. Vac. Sci. Technol. B 18 (4), pp. 1866-1873, 2000), there are some limitations on the type of structures patternable by these techniques. For instance, it is quite challenging to fabricate such a multilayer structure using NIL, due to difficulties such as: (a) solvent intermixing between layers; (b) deformation of the underlying layer during the imprinting of the top layer due to relatively high temperature and pressure; (c) a requirement that the subsequent layer have a lower Tg than the underlaying layer, in the case of polymeric materials; and (d) limited choice of materials that are imprintable, for instance, in one example, a bilayer or tri-layer resist with different properties are required; in another example, a crosslinked polymer is required to be the underlying layer (Z. Yu, H. Gao, W. Wu, H. Ge and S. Y. Chou, J. Vac. Sci. Technol. B 21 (6), pp. 2874-2877, 2003).
While multilayer structures have been demonstrated, as a result of the above-described limitations, the yield is typically very low and the types of polymer used in the layers is quite limited. Accordingly, an improved method of NIL capable of making multi-layer structures in high yield, and with minimal material restrictions, would be highly desirable.